Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $71.50   5.680%   $75.5612   $75.56   $75.55   $75.60  
  Purchase #2 $11.67   8.558%   $12.6687   $12.67   $12.65   $12.70  
  Purchase #3 $206.91   6.286%   $219.9164   $219.92   $219.90   $219.90  
  Purchase #4 $89.53   5.849%   $94.7666   $94.77   $94.75   $94.80  
  Purchase #5 $152.63   5.306%   $160.7285   $160.73   $160.75   $160.70  
  Purchase #6 $178.30   12.469%   $200.5322   $200.53   $200.55   $200.50  
  Purchase #7 $226.76   9.343%   $247.9462   $247.95   $247.95   $247.90  
  7 purchase totals = $937.30       $1,012.1198   $1,012.13   $1,012.10   $1,012.10